The present invention relates to compositions suitable for golf ball constructions and to golf balls which employ such compositions. Specifically, these compositions comprise graft copolymers and preferably include polyamide-ionomer graft copolymers.
Modern golf balls typically employ ionomeric resins as cover materials. Ionomeric resins, as a result of their toughness, durability, and wide range of hardness values, have become materials of choice for golf ball covers over traditional rubbers. Ionomeric resins generally comprise an alpha-olefin and an alpha, beta ethylenically unsaturated mono- or dicarboxylic acid neutralized with metal ions to the extent desired. Olefins which have been employed to prepare ionomeric resins include ethylene, propylene, butene-1 and the like. Unsaturated carboxylic acids which have been employed to prepare ionomeric resins include acrylic, methacrylic, ethacrylic, o-chloroacrylic, crotonic, maleic, fumaric, itaconic and the like. Ionomeric resins include copolymers of ethylene with acrylic acid such as those sold by Exxon Corporation under the trademark xe2x80x9cIOTEKxe2x80x9d, as well as copolymers of ethylene with methacrylic acid such as those sold by E.I. DuPont Nemours and Company under the trademark xe2x80x9cSURLYNxe2x80x9d. In some instances, a softening comonomer such as an acrylate ester has been included such that the ionomeric copolymer is an ionomeric terpolymer. Although various compositions have been employed to provide golf balls of varying playability characteristics, a need continues for compositions and covers which can be employed to provide golf balls which exhibit good playability and durability.
Generally, polyamides are polymers that contain recurring amide groups as integral parts of the main polymer chains. Amides are closely related to carboxylic acids. In a simple amide, the OH group of the carboxylic acid is replaced by an NH2 group. Polyamides are frequently referred to by their generic term xe2x80x9cnylons.xe2x80x9d Nylons are used in the production of synthetic fibers and engineering resins. A variety of polyamides exist including aromatic polyamides, polyamide fibers, and plastic polyamides.
There are no commercially available golf balls which are generally known to contain nylon. Nylon alone would be too brittle for use in a golf ball cover. When efforts have been made in other fields to blend nylon with softer materials some degree of incompatibility often has resulted, rendering the blends susceptible to cracking and premature failure. U.S. Pat. No. 4,690,981, the contents of which are incorporated herein by reference, shows soft terpolymer ionomers of ethylene/unsaturated carboxylic acid/softening comonomer which are useful in injection-molded items such as ski boots, ice skate shells, as coatings for fabrics, and as a replacement for balata in golf balls. The unsaturated carboxylic acid may be, for example, acrylic acid and methacrylic acid. The softening comonomer is, for example, an alkyl acrylate such as n-butyl acrylate. The ""981 patent briefly mentions that the ionomers can be blended with other materials such as nylon, polypropylene, propylene-ethylene copolymers, linear polyethylene, and ethylene/unsaturated carboxylic acid copolymers. However, there is no indication that blends can be used for golf balls.
In view of known strength and durability properties of nylon, it would be desirable to somehow utilize nylon in the construction of a golf ball. Specifically, it would be desirable to identify particular types of nylon materials that might be uniquely adapted to serve as materials for golf ball construction. There is a particular need for improved golf ball cover materials.
The present invention achieves the above-noted objectives and provides, in a first aspect, a golf ball having a core and a cover disposed about the core in which at least one of the core and the cover includes a composition comprising a polyamide-ionomer graft copolymer.
In another aspect, the present invention provides a golf ball comprising a core, at least one mantle layer disposed about the core and a cover disposed about the mantle layer. At least one of the core, the mantle layer, and the cover includes a polyamide-ionomer graft copolymer. The mantle layer may include one or more layers. Moreover, the golf ball may comprise one or more other intermediate layers disposed between the core and the cover.
In another aspect, the present invention provides a golf ball comprising a cover and a centrally disposed core. The core and/or the cover includes a composition blend comprising a polyamide-ionomer graft copolymer and an ionomer.
In yet another aspect, the present invention provides a golf ball comprising a core, a mantle layer disposed about the core, and a cover layer disposed about the mantle layer. Any of the core, the mantle layer, or the cover comprises a blend composition. The blend composition comprises a polyamide-ionomer graft copolymer and an ionomer.
In a further aspect, the present invention provides a method of making a golf ball comprising the steps of obtaining a golf ball core and forming a cover layer about the core. The core and/or the cover layer includes a resin composition comprising a graft copolymer of a polyamide component and an ionomeric component.
In still another aspect, the present invention provides a method for making a golf ball that includes the steps of obtaining a golf ball core, molding a mantle layer over the core to form an intermediate golf ball, and forming a cover layer over the intermediate golf ball. At least one of the core, the mantle layer, and the cover includes a graft copolymer comprising a polyamide component and an ionomeric component.
In anther aspect, the present invention provides a method of making a golf ball which includes the steps of obtaining a golf ball core and forming a cover layer over the core. At least one of the core and the cover comprises a composition blend. The composition blend comprises a polyamide-ionomer graft copolymer and an ionomer.
In yet another aspect, the present invention provides a method for making a golf ball that includes obtaining a golf ball core, forming a mantle layer about the core, and forming a cover layer about the mantle layer. Any of the core, the mantle layer, and the cover includes a composition comprising a blend of a polyamide-ionomer graft copolymer and an ionomer.
The invention comprises the several steps and the relation of one or more such steps with respect to each of the others, and the article possessing the features, properties and the relation of elements exemplified in the following detailed disclosure.